Ultraviolet radiation absorbents for thermoplastic polymers and methods of producing same

ABSTRACT

An ultraviolet radiation absorbent for thermoplastic polymer materials such as polyethylene terephthalate or polycarbonate contains cyclic imino ester compound of a specified structure in an amount of over 99.5 weight % and less than 100 weight %, having the melt beginning temperature obtained by melting point measurement in differential thermal analysis within the range of 300-310° C. and/or the weight loss beginning temperature obtained by thermogravimetric measurement within the range of 270-305° C.

BACKGROUND OF THE INVENTION

[0001] This invention relates to ultraviolet radiation absorbents for thermoplastic polymers and method of producing such absorbents. Films and various kinds of molded products such as boxes made of thermoplastic polymer materials undergo quality degradation such as discoloration and fading when exposed to ultraviolet radiation. Different kinds of ultraviolet radiation absorbents have therefore been in use for preventing such quality degradation for thermoplastic polymers as well as products made from them. The present invention relates to improvement in such ultraviolet radiation absorbents and methods of producing such improved absorbents.

[0002] Benzophenone compounds, benzotriazole compounds and salicylic acid compounds have been generally used as an ultraviolet radiation absorbent for thermoplastic polymers but it has been a problem that these absorbents are usually low in resistance against heat. In view of this problem, cyclic imino ester compounds have been proposed as ultraviolet radiation absorbents with improved heat resistance (U.S. Pat. No. 4,446,262, Japanese Patent Publications Tokko 62-5944 and 62-31027). These absorbents are themselves more resistant against heat but still have the problem that, when they are added or mixed to a thermoplastic polymer material such as polyethylene terephthalate or polycarbonate, they tend to adversely affect the original material characteristics of these thermoplastic polymers such as transparency. They also have the problem of sublimating and adversely affecting the workability and the environmental conditions during the mixing and molding processes when used for such thermoplastic polymer materials having high mixing and molding temperatures.

SUMMARY OF THE INVENTION

[0003] It is therefore an object of this invention to provide improved infrared radiation absorbents which are themselves highly resistant against heat, capable of producing products having the original material characteristics of thermoplastic polymers such as transparency when added and mixed with them without adversely affecting the workability or the environmental conditions. The invention also relates to methods of producing such absorbents.

[0004] The invention is based on the discovery by the present inventors as a result of their diligent investigations that absorbents containing cyclic imino ester compounds of a specified type in a specified amount and having a melt beginning temperature and/or a weight loss beginning temperature obtained under a specified condition adjusted within a specified range accomplish the aforementioned and other objects.

DETAILED DESCRIPTION OF THE INVENTION

[0005] The invention relates to an ultraviolet radiation absorbent for thermoplastic polymer materials containing cyclic imino ester compound shown by Formula 1 given below in an amount of over 99.5 weight % and less than 100 weight % and prepared such that at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C. is satisfied, where

[0006] The invention also relates to a method of producing an ultraviolet radiation absorbent comprising Steps A, B and C, Step A being a process of separating a solid component containing N,N′-bis(o-carboxyphenylterephthalamid) generated by amidation of anthranilic acid and terephthaloyl dichloride in the presence of a solvent and an alkali, Step B being a process of separating a solid component containing cyclic imino ester compound shown by Formula 1 generated by iminoesterification of N,N′-bis(o-carboxyphenylterephthalamid) within the solid component separated in Step A and acetic anhydride in the presence of a solvent, and Step C being a process of processing the solid component separated in Step B with an alkaline solution and further washing with water to obtain an ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.5 weight % and less than 100 weight %t and prepared such that at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C. is satisfied.

[0007] The invention further relates to a method of producing an ultraviolet radiation absorbent comprising Steps a and b, Step a being a process of separating a solid component cyclic imino ester compound shown by Formula 1 generated by iminoesterification of isatoic anhydride and terephthaloyl dichloride in the presence of a solvent and an alkali, and Step b being a process of processing the solid component separated in Step a with an alkaline solution and further washing with water to obtain an ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.5 weight % and less than 100 weight % and prepared such that at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C. is satisfied. In the description of the invention that follows, “cyclic imino ester compound shown by Formula 1” will be simply referred to as “cyclic imino ester”, the “melt beginning temperature obtained by melting point measurement in differential thermal analysis” will be simply referred to as the “melt beginning temperature”, and the “weight loss beginning temperature obtained by thermogravimetric measurement” will be simply referred to as the “weight loss beginning temperature.”

[0008] Ultraviolet radiation absorbents of this invention are not limited by the method of preparation. They may be prepared by (1) the method of adjusting the content of cyclic imino ester and the melt beginning temperature and/or the weight loss beginning temperature of the product to be within the specified range in the process of producing cyclic imino ester as it is being produced, or (2) the method of adjusting the content of cyclic imino ester and the melt beginning temperature and/or the weight loss beginning temperature of by adding a substance such as terephthalic acid, isophthalic acid, anthranilic acid and isatoic acid to the produced substantially pure cyclic imino ester such that the content of cyclic imino ester, the melt beginning temperature and/or the weight loss beginning temperature will be adjusted to be within the specified range. Of these two, however, the first is preferable from the point of view of cost of production. When the first method is used to adjust the content of cyclic imino ester, the melt beginning temperature and/or the weight loss beginning temperature, this method of adjustment is not intended to limit the scope of the invention, but the aforementioned methods through Steps A, B and C and through Steps a and b are preferable.

[0009] The method through Steps A, B and C is explained first. Step A is a process of amidation of anthranilic acid and terephthaloyl dichloride in the presence of a solvent and an alkali and separating a solid component containing N,N′-bis(o-carboxyphenylterephthalamid). There is no particular limitation as to the ratio between anthranilic acid and terephthaloyl dichloride used for the amidation process but it is preferable to use 0.49-0.51 moles, and more preferably 0.5 moles, of terephthaloyl dichloride per one mole of anthranilic acid. Neither is there any particular limitation regarding the solvent but acetone, methylethyl ketone, water and their mixtures are preferred as the solvent for anthranilic acid. As for terephthaloyl dichloride, a non-protonic solvent such as acetone and xylene is preferable. Examples of alkali include (1) hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, (2) carbonates of alkali metals such as sodium carbonate and potassium carbonate, (3) hydrogencarbonates of alkali metals such as sodium hydrogencarbonate and potassium hydrogencarbonate and (4) organic alkalis such as pyridine, but a choice should be made depending on the solvent to be used such that it will be dissolved in the solvent. The amount of the alkali to be used must be sufficient for completely neutralizing the hydrochloric acid produced as by-product in the amidation reaction. The reaction temperature should preferably be 10-80° C. and more preferably 20-50° C. The method of adding a solution of terephthaloyl dichloride to a liquid mixture or slurry of anthranilic acid and an alkali for the amidation is preferable.

[0010] In Step A, N,N′-bis(o-carboxyphenylterephthalamid) is obtained by an amidation reaction of anthranilic acid and terephthaloyl dichloride. The reaction system containing N,N′-bis(o-carboxyphenylterephthalamid) thus produced may be in the form of a slurry or a solution, depending on the kind of the solvent and the alkali which are used. If it is in the form of a slurry, a solid component containing N,N′-bis(o-carboxyphenylterephthalamid) is separated by filtering or centrifigation. If it is in the form of a solution, a solid component containing N,N′-bis(o-carboxyphenylterephthalamid) is separated by distilling away the solvent. The solid component thus separated may be directly used in Step B or may be washed with water for removing the by-product salts to a certain extent and then dried to be used in Step B.

[0011] The solid component separated in Step A is used in Step B for an iminoesterification reaction between N,N′-bis(o-carboxyphenylterephthalamid) in the solid component and acetic anhydride in the presence of a solvent to separate a solid component containing cyclic imino ester. The ratio of N,N′-bis(o-carboxyphenylterephthalamid) in the solid component and acetic anhydride used for the iminoesterification is usually 4-20 moles, and preferably 5-10 moles, of acetic acid per one mole of N,N′-bis(o-carboxyphenylterephthalamid). There is no particular limitation regarding the solvent but aromatic hydrocarbons such as toluene and xylene are preferable. The reaction temperature is preferably 100-180° C. and more preferably 110-140° C. As for the method of the reaction, it is preferable to carry out the iminoesterification with reflux by adding acetic anhydride and the solvent to the solid component separated in Step A.

[0012] In Step B, cyclic imino ester is generated by the iminoesterification reaction between N,N′-bis(o-carboxyphenylterephtbalamid) and acetic anhydride. The reaction system containing cyclic imino ester thus generated is in the form of a slurry. In Step B, a solid component containing cyclic imino ester is separated from such a slurry by filtering or centrifugation.

[0013] In Step C, the solid component separated in Step B containing cyclic imino ester is processed with an alkaline solution and washed with water to obtain an ultraviolet radiation absorbent comprising a product prepared so as to contain cyclic imino ester in an amount of over 99.5 weight % and less than 100 weight % and to have its melt beginning temperature adjusted to 300-310° C. and/or its weight loss beginning temperature adjusted to 270-305° C.

[0014] The method of adjusting the content of cyclic imino ester and the melt beginning temperature and/or weight loss temperature of the solid component containing cyclic imino ester in Step C by an alkali treatment and washing with water will be explained next. A slurry is prepared by adding water, acetone or an aqueous organic solvent such as methanol or a mixture thereof is added to the solid component containing cyclic imino ester separated in Step B by using a filter such as a Nutsche filter, an Oliver vacuum filter or a filter press or a centrifuge such as a basket type centrifuge or a centrifugal decanter such that the concentration of the solid component will be 20-30 weight %. Thereafter, an alkali treatment process is carried out by adding a required amount of an alkali to this slurry and stirring for 1-2 hours at 10-40° C. such that by-products and intermediate products can be easily removed in the subsequent process of washing with water. Next, after the solid component containing cyclic imino ester is separated from the alkali-treated slurry, the separated solid component is washed with water.

[0015] There is no particular limitation as to the kind of alkali to be used for this alkali treatment. Examples of alkali which may be used for this purpose include (1) alkoxides of alkali metals such as sodium methoxide, sodium ethoxide and potassium methoxide, (2) hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, (3) carbonates of alkali metals such as sodium carbonate and potassium carbonate, (4) hydrogencarbonates of alkali metals such as sodium hydrogencarbonate and potassium hydrogencarbonate, (5) ammonia water and (6) lower alkyl quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide. Of these, inorganic salts of alkali metals such as sodium hydroxide and sodium carbonate are preferable.

[0016] Neither is there any particular limitation as to the process of washing with water. As to the quantity of water to be used, it is preferable to use about 3-20 times the weight of the solid component and more preferably about 5-10 times. The water temperature should be preferably 20-80° C.

[0017] After the solid component containing cyclic imino ester is treated with an alkali and washed with water, it is separated and dried, and its content of cyclic imino ester and melt beginning temperature and/or weight loss beginning temperature are measured in order to ascertain that they are within the desired ranges. If the measurements show that the content of cyclic imino ester is too low or that the melt beginning temperature and/or the weight loss beginning temperature is too low, the aforementioned alkali treatment and the process of washing with water are repeated.

[0018] After Steps A, B and C are carried out as explained above, an ultraviolet radiation absorbent comprising a product which contains cyclic imino ester in an amount of over 99.5 weight % and less than 100 weight % and has its melt beginning temperature adjusted to 300-310° C. and/or its weight loss beginning temperature adjusted to 270-305° C. is obtained. In Step C, however, it is preferable to obtain a product containing cyclic imino ester in an amount of over 99.9 weight % and less than 100 weight % and 10 having its melt beginning temperature adjusted to 305-309° C. or its weight loss beginning temperature adjusted to 290-300° C., and is even more preferable to obtain a product containing cyclic imino ester in an amount of over 99.9 weight % and less than 100 weight % and having both its melt beginning temperature adjusted to 305-309° C. and its weight loss beginning temperature adjusted to 290-300° C.

[0019] Next, the method through Steps a and b is explained. Step a is a process of separating a solid component containing cyclic imino ester generated by iminoesterification of isatoic anhydride and terephthaloyl dichloride in the presence of a solvent and an alkali. There is no particular limitation as to the ratio between isatoic anhydride and terephthaloyl dichloride used for the iminoesterification but it is preferable to use 0.95-1.05 moles of terephthaloyl dichloride per 2 moles of isatoic anhydride. Neither is there any particular limitation regarding the solvent. Non-protonic solvents containing nitrogen such as dimethyl formaldehyde and dimethyl acetoamide, ketone solvents such as acetone and methylethyl ketone, ether solvents such as tetrahydrofuran and dioxane, and their mixtures are examples that may be used but acetone is preferred. Neither is there any particular limitation regarding the alkali. Examples include (1) hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, (2) lower alkyl quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide and (3) organic alkalis such as pyridine, but pyridine is preferred. An appropriate kind of alkali should be used, depending on the selected kind of solvent, so as to be dissolved in the selected kind of solvent. The amount of the alkali to be used is preferably selected such that the hydrochloric acid generated as by-product in the iminoesterification will be 100% neutralized. The reaction temperature should preferably be 10-80° C. and more preferably 20-50° C. As for the method of the reaction, it is preferable to add a solution of terephthaloyl dichloride to a mixed solution or slurry of isatoic anhydride for iminoesterification.

[0020] In Step a, cyclic imino ester is generated by iminoesterification of isatoic anhydride and terephthaloyl dichloride. The reaction system containing cyclic imino ester thus generated is either in the form or a slurry or in the form of a solution, depending on the kinds of the solvent and the alkali which have been used. If it is in the form of a slurry, the solid component containing cyclic imino ester is separated by filtering or by centrifugation. If it is in the form of a solution, the solvent is distilled away to separate the solid component containing cyclic imino ester. The solid component thus separated may be directly used in Step b or may be washed with water in order to remove by-product salts to a certain extent and dried before being used in Step b.

[0021] In Step b, the solid component containing cyclic imino ester separated in Step a is treated with an alkali and then washed with water to obtain an ultraviolet radiation absorbent comprising a product containing cyclic imino ester in an amount of over 99.5 weight % and less than 100 weight % and prepared such that its melt beginning temperature is adjusted to 300-310° C. and/or its weight loss beginning temperature is adjusted to 270-305° C. Thus, Step b is the same as aforementioned Step C.

[0022] In this manner, an ultraviolet radiation absorbent, comprising a product containing cyclic imino ester in an amount of over 99.5 weight % and less than 100 weight % and prepared such that its melt beginning temperature is adjusted to 300-310° C. and/or its weight loss beginning temperature is adjusted to 270-305° C. In Step b, however, it is preferable to obtain a product containing cyclic imino ester in an amount of over 99.9 weight % and less than 100 weight % and having its melt beginning temperature adjusted to 305-309° C. or its weight loss beginning temperature is adjusted to 290-300° C., and it is even more preferable to obtain a product containing cyclic imino ester by over 99.9 weight % and less than 100 weight % and having both its melt beginning temperature adjusted to 305-309° C. and its weight loss beginning temperature adjusted to 290-300° C.

[0023] The invention does not place any particular limitation on the kind of thermoplastic polymers to which ultraviolet radiation absorbents as described above should be applied. Examples of thermoplastic polymers to which they may be applied include (1) thermoplastic polyesters such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, (2) polycarbonates, (3) styrene polymers such as polystyrene, styrene-acrylnitrile-butadien copolymers and high-impact polystyrene, (4) acryl polymers, (5) amid polymers, (6) polyphenylene ether, (7) polyolefins such as polyethylene, polypropylene and vinyl polychloride, (8) polyoxymethylene, (9) polyphenylene sulfide, (10) lactic acid polymers and (11) mixtures of these thermoplastic polymers. Absorbents according to this invention are particularly effective when added to and mixed with polyethylene terephthalate and polycarbonates which have high transparency and require a high mixing temperature and a high molding temperature.

[0024] Ultraviolet radiation absorbents for thermoplastic polymers embodying this invention are themselves highly resistance against heat and can be added to and mixed with thermoplastic polymers such as polyethylene terephthalate and polycarbonates requiring a high mixing temperature and a high molding temperature to produce molded products having the same high transparency originally possessed by these thermoplastic polymers. They do not adversely affect the workability or the environmental condition in the mixing and molding processes even when added to and mixed with thermoplastic polymers such as polyethylene terephthalate and polycarbonates requiring a high mixing temperature and a high molding temperature.

[0025] The invention does not particularly limit the amount of the absorbent to be used. When it is applied to thermoplastic polymers, the ratio is usually 0.1-5 weight parts to 100 weight parts of thermoplastic polymers.

[0026] The invention is described next with reference to the following ten embodiments.

[0027] (1) Ultraviolet radiation absorbent containing cyclic imino ester by 99.99 weight % and having its melt beginning temperature adjusted to 309° C.

[0028] (2) Ultraviolet radiation absorbent containing cyclic imino ester by 99.98 weight % and having its melt beginning temperature adjusted to 307° C.

[0029] (3) Ultraviolet radiation absorbent containing cyclic imino ester by 99.96 weight % and having its melt beginning temperature adjusted to 305° C.

[0030] (4) Ultraviolet radiation absorbent containing cyclic imino ester by 99.88 weight % and having its melt beginning temperature adjusted to 301° C.

[0031] (5) Ultraviolet radiation absorbent containing cyclic imino ester by 99.99 weight % and having its weight loss beginning temperature adjusted to 304° C.

[0032] (6) Ultraviolet radiation absorbent containing cyclic imino ester by 99.98 weight % and having its weight loss beginning temperature adjusted to 300° C.

[0033] (7) Ultraviolet radiation absorbent containing cyclic imino ester by 99.97 weight % and having its weight loss beginning temperature adjusted to 290° C.

[0034] (8) Ultraviolet radiation absorbent containing cyclic imino ester by 99.89 weight % and having its weight loss beginning temperature adjusted to 271° C.

[0035] (9) Ultraviolet radiation absorbent containing cyclic imino ester by 99.97 weight % and having its melt beginning temperature adjusted to 306° C. and its weight loss beginning temperature adjusted to 300° C.

[0036] (10) Ultraviolet radiation absorbent containing cyclic imino ester by 99.98 weight % and having its melt beginning temperature adjusted to 307° C. and its weight loss beginning temperature adjusted to 298° C.

[0037] The invention is described next by way of examples but it goes without saying that these examples are not intended to limit the scope of the invention. In what follows, “part” will be mean “weight part” and “%” will mean “weight%”.

[0038] Part 1 (Preparation of Ultraviolet Radiation Absorbents for Thermoplastic Polymers: No.1)

TEST EXAMPLE 1

[0039] Anthranilic acid 13.7 g (0.1 moles), anhydrous sodium carbonate 5.19 g (0.049 moles) and water 100 ml were placed in a flask with four openings provided with a thermometer, a stirrer, a reflux cooler and a dropper funnel and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 300 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 19.8 g was obtained. The dried solid component 19.8 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask with four openings for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 17.6 g containing cyclic imino ester was obtained. Finally, this solid component 17 g and water 68 g were placed in the flask and 1% aqueous solution of sodium hydroxide 2.3 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 160 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 16.5 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.99%, and its melt beginning temperature was 309° C. This will be referred to as Absorbent (P-1).

[0040] The content of cyclic imino ester was measured by high performance liquid chromatography using chloroform as the elution liquid and a UV detector for detection. The melt beginning temperature was measured by using a differential thermal analyzer (TAS200 produced by Rigaku Co., Ltd). The ultraviolet radiation absorbent for thermoplastic polymers (P-1) 10 mg was measured and placed in a sample pan and a DTA curve was obtained by raising the temperature at the rate of 5° C. per minute in a nitrogen atmosphere. The crossing point was obtained between the tangent line extended from the base line of this DTA curve and the tangent line extended from the peak line to determined the melt beginning temperature. Throughout herein, content of cyclic imino ester and melt beginning temperatures are obtained similarly.

TEST EXAMPLE 2

[0041] Anthranilic acid 13.7 g (0.1 moles), pyridine 7.74 g (0.098 moles) and acetone 200 ml were placed in a flask with four openings as in Test Example 1, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 100 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 18.2 g was obtained. The dried solid component 18.2 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask with four openings for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 14.8 g containing cyclic imino ester was obtained. Finally, this solid component 14 g and methanol 68 g were placed in the flask and 1% solution of sodium methoxide methanol 2.14 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 140 g at 40° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 13.4 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.98%, and its melt beginning temperature was 307° C. This will be referred to as Absorbent (P-2).

TEST EXAMPLE 3

[0042] Isatoic anhydride 16.3 g (0.1 moles), pyridine 7.74 g (0.098 moles) and acetone 200 ml were placed in a flask with four openings as in Test Example 1, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 100 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing cyclic imino ester was obtained by iminoesterification for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 15.8 g containing cyclic imino ester was obtained. The dried solid component 15 g and water 48 g were placed in the flask and 1% aqueous solution of sodium carbonate 3.96 g was added with stirring and an alkali treatment was effected at 30° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 130 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.4 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.96%, and its melt beginning temperature was 305° C. This will be referred to as Absorbent (P-3).

TEST EXAMPLE 4

[0043] Anthranilic acid 13.7 g (0.1 moles), potassium hydroxide 5.32 g (0.095 moles) and water 100 ml were placed in a flask with four openings as in Test Example 1, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 200 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 19.8 g was obtained. The dried solid component 19.8 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, a solid component 15.4 g containing cyclic imino ester was obtained. This dried solid component 15 g and water 35 g were placed in the flask and 1% aqueous solution of potassium hydroxide 7.75 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 160 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.4 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.88%, and its melt beginning temperature was 301° C. This will be referred to as Absorbent (P-4).

COMPARISON EXAMPLE 1

[0044] Absorbent (P-1) obtained in Test Example 1 10 g and 1×10⁻²% aqueous solution of sodium hydroxide 1000 ml were placed in a beaker. After it was stirred for one hour with a mixer, a solid component was filtered. The filtered solid component and water 1000 ml were placed in a beaker, and after it was stirred for one hour with a mixer, a solid component was filtered. This routine was repeated three times and the solid component thus obtained was dried for one hour at 100° C. to obtain yellowish powder. This yellowish powder was analyzed and found to contain cyclic imino ester by 100.00%, and its melt beginning temperature was 311° C. This will be referred to as Absorbent (R-1).

COMPARISON EXAMPLE 2

[0045] Yellowish powder 16.9 g was obtained in the same way as in Test Example 1 except that the alkali treatment was dispensed with. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.01%, and its melt beginning temperature was 295° C. This will be referred to as Absorbent (R-2).

[0046] Part 2 (Preparation of Ultraviolet Radiation Absorbents for Thermoplastic Polymers: No.2)

TEST EXAMPLE 5

[0047] Anthranilic acid 13.7 g (0.1 moles), anhydrous sodium carbonate 5.19 g (0.049 moles) and water 100 ml were placed in a flask with four openings provided with a thermometer, a stirrer, a reflux cooler and a dropper funnel and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 300 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 19.6 g was obtained. The dried solid component 19.6 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask with four openings for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 17.2 g containing cyclic imino ester was obtained. Finally, this solid component 17 g and water 68 g were placed in the flask and 1% aqueous solution of sodium hydroxide 2.66 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 160 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 16.5 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.99%, and its weight loss beginning temperature was 304° C. This will be referred to as Absorbent (P-5).

[0048] The weight loss beginning temperature was measured by using a thermogravimetric analyzer (TAS200 produced by Rigaku Co., Ltd). Absorbent (P-5) 10 mg was measured and placed in a sample pan and a TG curve was obtained by raising the temperature at the rate of 5° C. per minute in a nitrogen atmosphere. The point at which the curve separates from the base line was determined as the weight loss beginning temperature. Throughout herein, weight loss beginning temperatures are obtained similarly.

TEST EXAMPLE 6

[0049] Anthranilic acid 13.7 g (0.1 moles), pyridine 7.74 g (0.098 moles) and acetone 200 ml were placed in a flask with four openings as in Test Example 5, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 100 ml was dropped into this flask by means of the dropping funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was filtered out from this slurry and after it was washed with water 300 ml and dried, a dried solid component 17.9 g was obtained. The dried solid component 17.9 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask with four openings for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 15.1 g containing cyclic imino ester was obtained. Finally, this solid component 14 g and methanol 68 g were placed in the flask and 1% solution of sodium methoxide methanol 2.01 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 140 g at 40° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 13.5 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.98%, and its weight loss beginning temperature was 300° C. This will be referred to as Absorbent (P-6).

TEST EXAMPLE 7

[0050] Isatoic anhydride 16.3 g (0.1 moles), pyridine 7.74 g (0.098 moles) and acetone 200 ml were placed in a flask with four openings as in Test Example 5, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 100 ml was dropped into this flask by means of the dropping funnel over one hour at room temperature, a slurry with solid component containing cyclic imino ester was obtained by iminoesterification for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 16.1 g containing cyclic imino ester was obtained. The dried solid component 15 g and water 48 g were placed in the flask and 1% aqueous solution of sodium carbonate 4.66 g was added with stirring and an alkali treatment was effected at 30° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 130 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.3 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.97%, and its weight loss beginning temperature was 290° C. This will be referred to as Absorbent (P-7).

TEST EXAMPLE 8

[0051] Anthranilic acid 13.7 g (0.1 moles), potassium hydroxide 5.32 g (0.095 moles) and water 100 ml were placed in a flask with four openings as in Test Example 5, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 200 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 19.7 g was obtained. The dried solid component 19.7 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 15.5 g containing cyclic imino ester was obtained. This dried solid component 15 g and water 35 g were placed in the flask and 1% aqueous solution of potassium hydroxide 7.16 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 160 g at 60° C. The washed solid component was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.1 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.89%, and its weight loss beginning temperature was 271° C. This will be referred to as Absorbent (P-8).

COMPARISON EXAMPLE 3

[0052] Absorbent (P-5) obtained in Test Example 5 10 g and 1×10⁻²% aqueous solution of sodium hydroxide 1000 ml were placed in a beaker. After it was stirred for one hour with a mixer, a solid component was filtered. The filtered solid component and water 1000 ml were placed in a beaker, and after it was stirred for one hour with a mixer, a solid component was filtered. This routine was repeated three times and the solid component thus obtained was dried for one hour at 100° C. to obtain yellowish powder. This yellowish powder was analyzed and found to contain cyclic imino ester by 100.00%, and its weight loss beginning temperature was 308° C. This will be referred to as Absorbent (R-3).

COMPARISON EXAMPLE 4

[0053] Yellowish powder 16.5 g was obtained in the same way as in Test Example 5 except that the alkali treatment was dispensed with. This yellowish powder was analyzed and found to contain cyclic imino ester by 98.94%, and its weight loss beginning temperature was 260° C. This will be referred to as Absorbent (R-4).

[0054] Part 3 (Preparation of Ultraviolet Radiation Absorbents for Thermoplastic Polymers: No.3)

TEST EXAMPLE 9

[0055] Isatoic anhydride 16.3 g (0.1 moles), pyridine 7.74 g (0.098 moles) and acetone 200 ml were placed in a flask with four openings provided with a thermometer, a stirrer, a reflux cooler and a dropper funnel and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 100 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing cyclic imino ester was obtained by iminoesterification for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 16.0 g containing cyclic imino ester was obtained. The dried solid component 15 g and water 48 g were placed in the flask and 1% aqueous solution of sodium carbonate 3.36 g was added with stirring and an alkali treatment was effected at 30° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 130 g at 60° C. After the washed solid component was dehydrated, it was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.4 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.97%. Its melt beginning temperature and weight loss beginning temperature were respectively 306° C. and 300° C. This will be referred to as Absorbent (P-9).

TEST EXAMPLE 10

[0056] Anthranilic acid 13.7 g (0.1 moles), anhydrous sodium carbonate 5.19 g (0.049 moles) and water 100 ml were placed in a flask with four openings as in Test Example 9, and the mixture was dissolved with stirring for 10 minutes. After a solution obtained by dissolving terephthaloyl dichloride 10.2 g (0.05 moles) in acetone 300 ml was dropped into this flask by means of the dropper funnel over one hour at room temperature, a slurry with solid component containing N,N′-bis(o-carboxyphenylterephthalamid) was obtained by amidation for one hour with reflux. A solid component was separated from this slurry and after it was washed with water 300 ml and dried, a dried solid component 19.8 g was obtained. The dried solid component 19.8 g, acetic anhydride 102 g (1 mole) and toluene 100 ml were placed in the flask with four openings for iminoesterification with reflux for 6 hours, and after it was cooled down to room temperature, the solid component was filtered out. After this filtered solid component was washed with acetone 100 ml and dried, a solid component 17.3 g containing cyclic imino ester was obtained. Finally, this solid component 15 g and water 48 g were placed in the flask and 1% aqueous solution of sodium hydroxide 3.47 g was added with stirring and an alkali treatment was effected at 25° C. for 30 minutes with stirring. The alkali-treated solid component was filtered out and washed with warm water 160 g at 60° C. After the washed solid component was dehydrated, it was dried for 2 hours with a hot-air drier at 100° C. to obtain yellowish powder 14.8 g. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.98%. Its melt beginning temperature and weight loss beginning temperature were respectively 307° C. and 298° C. This will be referred to as Absorbent (P-10).

COMPARISON EXAMPLE 5

[0057] Absorbent (P-10) obtained in Test Example 10 10 g and 1×10⁻²% aqueous solution of sodium hydroxide 1000 ml were placed in a beaker. After it was stirred for one hour with a mixer, a solid component was filtered. The filtered solid component and water 1000 ml were placed in a beaker, and after it was stirred for one hour with a mixer, a solid component was filtered. This routine was repeated three times and the solid component thus obtained was dried for one hour at 100° C. to obtain yellowish powder. This yellowish powder was analyzed and found to contain cyclic imino ester by 100.00%. Its melt beginning temperature and weight loss beginning temperature were respectively 311° C. and 308° C. This will be referred to as Absorbent (R-5).

COMPARISON EXAMPLE 6

[0058] Yellowish powder 15.1 g was obtained in the same way as in Test Example 10 except that the alkali treatment was dispensed with. This yellowish powder was analyzed and found to contain cyclic imino ester by 99.20%. Its melt beginning temperature and weight loss beginning temperature were respectively 297° C. and 266° C. This will be referred to as Absorbent (R-6).

[0059] Part 4 (Evaluation on Ultraviolet Radiation Absorption)

[0060] Each of the ultraviolet radiation absorbents 1.0 mg prepared in Parts 1, 2 and 3 was dissolved in 200 ml of 1,1,2,2-tetrachlorethane of the optical grade and transparency at 350 nm measured by using a UV-Vis spectrophotometer (U2000 produced by Hitachi, Ltd.) was evaluated according to the following standard.

[0061] A: Transparency less than 25%

[0062] B: Transparency greater than 25% but less than 26%

[0063] C: Transparency greater than 26%

[0064] The results are shown in Table 1.

[0065] Part 5 (Evaluation when Absorbents are Added and Mixed with Polyethylene Terephthalate)

[0066] Ultraviolet radiation absorbents prepared in Parts 1, 2 and 3 were evaluated regarding resistance against heat, transparency and workability when added to and mixed with polyethylene terephthalate with intrinsic viscosity 0.70. The results are shown in Table 1.

[0067] For evaluating resistance against heat, 100 parts of polyethylene terephthalate chips and 2 parts of each of the absorbents prepared in Parts 1-3 were subjected to a dry blending process and extruded while a double-axis extruder was used to mix them together at 280° C. After the mixture was cooled and made into pellets, they were dried in vacuum. The vacuum-dried pellets 10 g were put inside a test tube and prepared Samples B obtained by heating and melting for 10 minutes and Samples T obtained by heating and melting for 60 minutes. Both Samples B and T were checked visually and evaluated according to the following standard:

[0068] A: No difference between B and T and no abnormalities such as bums were observed on T

[0069] B: T is somewhat more yellowish than B but no abnormalities such as bums were observed on T

[0070] C: T is clearly more yellowish than B and bums were observed on parts of T

[0071] For evaluating transparency, 100 parts of polyethylene terephthalate chips and 2 parts each of the absorbents prepared in Parts 1-3 were subjected to a dry blending process and extruded from a T-die while a double-axis extruder was used to mix them together at 280° C. and cooled by means of a cooling roller at about 50° C. to produce non-crystalline sheets of thickness about 1 mm. Blank sheets were separately prepared in the same manner except without blending the ultraviolet radiation absorbents. Evaluation of transparency was carried out according to the following standard:

[0072] A: As transparent as the blanks

[0073] B: Very little more cloudy than the blanks

[0074] C: A little more cloudy than the blanks

[0075] D: Definitely more cloudy than the blanks

[0076] For the evaluation of workability, 100 parts of polyethylene terephthalate chips and 2 parts each of the absorbents prepared in Parts 1-3 were subjected to a dry blending process. Extrusion was repeated continuously for 6 hours while a double-axis extruder was used to mix them together at 280° C. Presence or absence of deposits at the vent opening of the extruder was visually checked one hour, 3 hours, and 6 hours after the starting of the extrusion and workability was evaluated according to the following standard:

[0077] A: Deposits not observed after 6 hours

[0078] B: Deposits not observed after 3 hours but observed after 6 hours

[0079] C: Deposits not observed after one hour but observed after 3 hours

[0080] D: Deposits observed after one hour

[0081] Part 6 (Evaluation when Absorbents are Added and Mixed with Polycarbonate)

[0082] Ultraviolet radiation absorbents prepared in Parts 1-3 were evaluated regarding resistance against heat, transparency and workability when added to and mixed with polycarbonate chips (Panlite, produced by Teijin Chemicals, Ltd). The results are shown in Table 1.

[0083] For evaluating resistance against heat, 100 parts of polycarbonate chips and 2 parts each of the absorbents prepared in Parts 1-3 were subjected to a dry blending process and a double-axis extruder was used to mix them together at 290° C. After the extrusion, it was cooled with water, made into pellets and dried in vacuum for 5 hours at 100° C. Evaluations were made as in Part 5.

[0084] For evaluating transparency, 100 parts of polycarbonate chips and 2 parts each of the absorbents prepared in Parts 1-3 were subjected to a dry blending process and a double-axis extruder was used to mix them together at 290° C. and they were extruded from a T-die and cooled by means of a cooling roller at about 50° C. to produce sheets of thickness about 1 mm. Evaluations were made as in Part 5.

[0085] For evaluating workability, 100 parts of polycarbonate chips and 2 parts each of the absorbents prepared in Parts 1 and 3 were subjected to a dry blending process. Extrusion was repeated continuously for 6 hours while a double-axis extruder was used to mix them together at 290° C. Evaluations were made as in Part 5. TABLE 1 Absorbent Kind/Con- Evaluations centration MBT WLBT PET PC (%) (° C.) (° C.) AB RH WK TR RH WK TR Test 1 P-1/99.99 309 — A B B A B B B 2 P-2/99.98 307 — A B A A B B A 3 P-3/99.96 305 — A B A A B A A 4 P-4/99.88 301 — B B A B B A B Comp 1 R-1/100.00 311 — A B D D B D D 2 R-2/99.01 295 — C D A D D A D Test 5 P-5/99.99 — 304 A B B A B B B 6 P-6/99.98 — 300 A B A A B B A 7 P-7/99.97 — 290 A B A A B A A 8 P-8/99.89 — 271 B B A B B A B Comp 3 R-3/100.00 — 308 A B D D B D D 4 R-4/98.94 — 260 C D A D D A D Test 9 P-9/99.97 306 300 A B A A B A A 10  P-10/99.98 307 298 A B A A B A A Comp 5 R-5/100.00 311 308 A B D D B D D 6 R-6/99.20 297 266 C D A D D A D

[0086] As can be understood from above; each of the absorbents of Test Examples 1-10 satisfies the requirements on the ability to absorb ultraviolet radiation, resistance against heat, transparency and workability. In particular, Test Examples 9 and 10 with concentration of cyclic imino ester greater than 99.9% and less than 100%, having the melt beginning temperature in the range of 305-309° C. and the weight loss beginning temperature in the range of 290-300° C. are excellent. By contrast, Comparison Examples 1, 3 and 5 are substantially purely cyclic imino ester without hardly any other substance and are poor in transparency and workability. Comparison Examples 2, 4 and 6 contain relatively large quantities of other substances and the content of cyclic imino ester is accordingly lower. They are inferior in the ability to absorb ultraviolet radiation and also poor in resistance against heat and transparency.

[0087] In summary, the absorbents according to this invention are themselves superior in resistance against heat and capable of being added to and mixed with thermoplastic polymers such as polyethylene terephthalate or polycarbonate to obtain molded products with the same transparent characteristic of the thermoplastic polymers, not adversely affecting the environmental conditions during the mixing and molding processes. 

What is claimed is:
 1. An ultraviolet radiation absorbent for thermoplastic polymer materials, said ultraviolet radiation absorbent containing cyclic imino ester compound shown by Formula 1 given below

in an amount of over 99.5 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C.
 2. The ultraviolet radiation absorbent of claim 1 containing the cyclic imino ester compound shown by Formula 1 in an amount of over 99.9 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C.
 3. The ultraviolet radiation absorbent of claim 2 containing the cyclic imino ester compound shown by Formula 1 in an amount of over 99.9 weight % and less than 100 weight % and satisfying both of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C.
 4. The ultraviolet radiation absorbent of claim 3 which is for polyethylene terephthalate.
 5. The ultraviolet radiation absorbent of claim 3 which is for polycarbonate.
 6. A method of producing an ultraviolet radiation absorbent, said method comprising Step A, Step B and Step C; said Step A being a process of causing an amidation of anthranilic acid and terephthaloyl dichloride in the presence of a solvent and an alkali to generate N,N′-bis(o-carboxyphenylterephthalamid) and separating a solid component containing N,N′-bis(o-carboxyphenylterephthalamid) generated by said amidation; said Step B being a process of separating a solid component containing cyclic imino ester shown by Formula 1 generated by iminoesterification of N,N′-bis(o-carboxyphenylterephthalamid) within the solid component separated in said Step A and acetic anhydride in the presence of a solvent; and said Step C being a process of processing the solid component separated in said Step B with an alkaline solution and further washing with water to obtain the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 given below

in an amount of over 99.5 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C.
 7. The method of claim 6 wherein said Step C is a process of obtaining the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.9 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C.
 8. The method of claim 7 wherein said Step C is a process of obtaining the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.9 weight % and less than 100 weight % and satisfying both of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C.
 9. A method of producing an ultraviolet radiation absorbent, said method comprising Step a and Step b; said Step a being a process of separating a solid component containing cyclic imino ester compound shown by Formula 1 given below

generated by iminoesterification of isatoic anhydride and terephthaloyl dichloride in the presence of a solvent and an alkali; and said Step b being a process of processing the solid component separated in said Step a with an alkaline solution and further washing with water to obtain the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.5 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 300-310° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 270-305° C.
 10. The method of claim 9 wherein said Step b is a process of obtaining the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula I in an amount of over 99.9 weight % and less than 100 weight % and satisfying at least one of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C.
 11. The method of claim 10 wherein said Step b is a process of obtaining the ultraviolet radiation absorbent for thermoplastic polymers containing cyclic imino ester compound shown by Formula 1 in an amount of over 99.9 weight % and less than 100 weight % and satisfying both of the conditions that the melt beginning temperature obtained by melting point measurement in differential thermal analysis be 305-309° C. and that the weight loss beginning temperature obtained by thermogravimetric measurement be 290-300° C. 